Fusiform Muscle:Spindle shaped (fat in the middle and thin at both ends) muscle in which the fibers are arranged parallel to the line from origin to insertion. They are tapered on the ends and thicker in the middle and the fasiculi (bundles of muscle fibers) end in flat tendons which attach the muscle to the bone.

Fusiform muscles typically are involved in movement over large ranges of motion and tend to be very strong due to the strength of the long bundles of muscles arranged parallel to each other and attached to relatively small origins and insertions. The biceps brachii is a fusiform muscle.

Fusiform Muscle
P.C.S stands for physiological cross-section.

Since a fusiform muscle has no pennation, calculating the physiological cross-section area (PCSA) is relatively straight-forward. It can be determined by dividing the volume of the muscle (cm3) by the product of muscle density (g x cm-3) and muscle length (cm).